A Manhattan real estate brokerage is taking the guessing game out of marketing with the creation of a system that tracks responses to online and offline ads.

The system, launched last year by Coldwell Banker Hunt Kennedy, a brokerage with about 300 agents and $1 billion in annual sales, uses a pool of unique phone numbers to track the telephone responses to a range of advertising sources, and also tracks Internet responses to ads.

That information is helping the company and individual agents to identify what works and doesn’t work i